Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include<iostream>
#include<vector>
#include<queue>
using namespace std;

const int INF = 1e9;

int main() {
	int h, w; cin >> h >> w;
	vector<string>s(h); for (auto&& x : s)cin >> x;
	
	int whiteSum = 0;
	for (int i = 0; i < h; i++) {
		for (int j = 0; j < w; j++) {
			if (s[i][j] == '.')whiteSum++;
		}
	}

	vector<vector<int>>dp(h, vector<int>(w, INF));
	queue<pair<int, int>>que;
	int gx = h - 1, gy = w - 1;
	que.push({ 0,0 });
	dp[0][0] = 1;
	int dx[4] = { -1,0,1,0 }, dy[4] = { 0,-1,0,1 };

	while (!que.empty()) {
		int x = que.front().first, y = que.front().second; que.pop();
		if (x == gx && y == gy)break;
		for (int i = 0; i < 4; i++) {
			int nx = x + dx[i], ny = y + dy[i];
			if (nx < 0 || nx >= h || ny < 0 || ny >= w || s[nx][ny] == '#' || dp[nx][ny] != INF)continue;
			que.push({ nx,ny });
			dp[nx][ny] = dp[x][y] + 1;
		}
	}
	int ans = whiteSum - dp[gx][gy];
	cout << (ans >= 0 ? ans : -1) << endl;

	return 0;
}